In both cases you have an assignment in the first line which is useless.

There are two ways to make it better, depending on whether the new DataTable() expression has side effects.

In the most frequent and good case, the allocation of a new DataTable in the first line can be omitted completely. You then write:

DataTable itemTable;
itemTable = //CODE

The first line declares the local variable. The second line assigns it. However, it is much more common to put these two things together in one statement, namely:

DataTable itemTable = //CODE

This is the one you should use.

Often you would use an implicit type with var. The variable will still be strongly typed:

var itemTable = //CODE

If the type of the expression //CODE is DataTable, this is entirely equivalent to what you had before. If the (compile-time) type of the right-hand side is instead something more specific, say YourItemDataTable, then using var will give the local variable that more specific type as well. That may very well be fine. So very often, it is appropriate to use var, but it is also a matter of style.

In the unlikely (theoretically possible) scenario where the initialization of a new object instance is intended and needed (a constructor may have side effects), C# allows a new-object expression to be a statement by itself. So in that case, write:

new DataTable();
DataTable itemTable = //CODE

The language has a support for this situation, but I doubt it is useful. When DataTable is the one in the System.Data.dll assembly, it is not relevant.

If another model has column names that are different from existing ones, there will be an exception in the CreatePredictionEngine method like this:
System.ArgumentOutOfRangeException
Could not find input column 'SentimentText'.

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This is my current code, which works fine for getting attributes/properties such as distinguishedName, userPrincipleName etc, but it returns a blank value.

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I have the following condition:
I have a windows Form (Not WPF). The DataGrid is in TabControl. I am adding the rows using array into it. When I click the Tab for viewing the grid, I am getting exceptions.

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